Placental transfer of IgG antibodies against Haemophilus influenzae type b capsular polysaccharide in Brazilian term and preterm newborns.

Placental transfer of antibodies to polysaccharide antigens is still a controversial subject. The incidence of invasive Haemophilus influenzae type b (Hib) infections is high in countries where the vaccine has not been included in routine immunization schedules. In the present work, we proposed to evaluate the natural immune response to Hib capsular polysaccharide in term and preterm Brazilian newborns and their respective mothers. Although the means, medians, and ranges of antibody titres in paired maternal and cord sera from preterm neonates were similar, the maternal levels were slightly higher than the cord levels and a poor correlation between these levels was verified. Term neonates showed similar antibody levels to those of their respective mothers and a very significant correlation between these levels was observed.